The present invention concerns a drive for the doors of a building of frame construction.
In wide use throughout the western United States are buildings, termed “pole buildings”, which serve primarily as storage structures for providing a large covered area for farm equipment and the storage of feed and supplies associated with farming. Such buildings are of low cost per square foot of construction and have large door openings enabling the storage of equipment including tractors, farm machinery and even light aircraft. The buildings are of light frame construction with wooden trusses and an exterior of corrugated sheet metal. The doors of such buildings comprise multiple panels in pairs suspended for travel into an open position whereat the panels overlap one another adjacent opposite sides of the building doorway. In view of such building being of frame construction the doors are necessarily of light weight construction but require considerable effort to open and close. Further complicating driven doors in such buildings is that the door panels are often of non-uniform width with travel of the sets of panels being unequal. An objective of the present invention is to position the door sets, of different widths and travel, to their open and their closed positions simultaneously.
A further problem with known powered door systems for buildings in general is the original cost of such systems which is a significant factor in the overall cost of building construction.
U.S. Pat. No. 6,352,097 discloses a door with multiple panels including sets each of two panels which move in sequence to open a building doorway. The panels are suspended from overhead rails. Travel in opposite directions is imparted to the two leading doors by parallel cable runs. Travel is imparted to each trailing door by a “bumper” carried by a pair of pulleys on a continuous element engaging a stop on a wall.
U.S. Pat. No. 2,878,532 is also of interest in that it discloses a pair of doors which move in unison along a track in opposite directions with the opening mechanism including a pair of slides. Of particular interest is a mechanism for disengaging one door from the drive mechanism to permit separate positioning of a door by manual effort.
U.S. Pat. No. 2,425,016 discloses multiple panels of a door which are interconnected by an auxiliary drive system for imparting trailing movement to a second and third panel of a door.
U.S. Pat. No. 3,120,683 discloses hanger doors fully supported by parallel tracks with grooved rollers entrained on the tracks.